There are various known processes for synthesizing polyanilines, which are typical aromatic amine polymers. They can be roughly classified into (i) chemical synthesis, and (ii) electrolytic oxidative polymerization. The chemical synthesis of polyanilines has been known for a long time, as reported by A. G. Green and A. E. Woodhead, J. Chem. Soc., 2388 (1910). This process is carried out by, for example, placing aniline in hydrochloric acid and adding ammonium persulfate, (NH.sub.4).sub.2 S.sub.2 O.sub.8, as an initiator. The resulting polyaniline is a powder. After it has been washed, collected, dried, etc., it is molded under pressure to form pellets which are ready for use. The electrolytic oxidative polymerization is carried out by dissolving aniline in an aqueous solution of a protonic acid, placing a "Nesa" glass electrode and a metal electrode in the solution, and applying a DC voltage or an electric current to cause the deposition of a polymer on the anode.
A great deal of attention has recently come to be paid to polyanilines as the materials for electrodes forming cells, since they exhibit excellent electrochemical properties. Studies have been directed particularly to the electrochemical synthesis of polyanilines, as in this way it is possible to produce polyanilines in layer form [A. G. MacDiarmid et al., Mol. Cryst. Lig. Cryst., Vol. 121 (1985), pp. 187-190].
The electrochemical synthesis of polyanilines, however, has a serious drawback. Although it is possible to form a good film as long as only a small quantity of electricity, say, up to 1 C (coulomb)/cm.sup.2, is employed, the passage of a larger quantity of electricity results in the formation of a mass of powder which is coherent on the electrode surface, but loses cohesion upon drying. This powder has a low apparent density and easily falls off the electrode. The use of a higher electric current results in a more powdery product.
Therefore, the electrochemically synthesized polyaniline is also essentially a powder when formed in a thick layer, and basically differs from other electrochemically synthesized conductive polymers, such as polythiophenes, polypyrroles and polyparaphenylenes. Therefore, the polyanilines have also been in pellets of like form as the electrode materials, but have been considered as being unable to achieve as high an output density as that which can be obtained by any other conductive polymer in film form. Accordingly, a great deal of research efforts have been made to realize polyanilines in film form. For example, Japanese Patent Application laid open under No. 149628/1985 states that the addition of amines and a substance forming ammonium ions is effective for the production of polyanilines by electrolytic oxidative polymerization.
An inorganic protonic acid is employed in any of the processes for the electrochemical synthesis of polyanilines as hereinabove described. However, the thick polyaniline film which is formed electrochemically by using a protonic acid such as sulfuric, perchloric, hydrochloric, tetrafluoroboric or nitric acid, is so low in adhesive strength that it falls off the substrate easily during washing, as hereinabove stated. It is also low in mechanical strength. When the conventional polyaniline is used for making a cell, it is necessary to mold it into pellets or like form, as it is essentially a powder, and the resulting cell has, therefore, an output strength which is lower than that of a cell formed from other conductive polymers.